Yes, studies are considered essential. Even CBSA was tweeting about that 'Work and Study' as one of the first essential reasons to enter Canada. I am just afraid they changed their criteria and added essential reason to travel. Hoping for the best.That is correct as of right now, study is considered essential.
I guess there are some rumors going around that online study will be considered non essential & you wont be able to travel even if you got the permit before 18th March but there is no such official confirmation now.